title: Long-term accelerated forgetting of verbal and non-verbal information in temporal lobe epilepsy.
abstract: BACKGROUND
  We investigated whether pre-surgical patients with temporal lobe epilepsy (TLE) forget verbal and non-verbal material faster than healthy controls over retention intervals of an hour and 6 weeks, and whether any observed memory loss was associated with structural changes to the hippocampus and/or seizure frequency.
  
  
  METHODS
  A mixed factorial design compared the performance of 27 patients with TLE and 22 healthy control participants, matched for IQ, age and gender, on tests of story recall and complex figure recall at three delays: immediate, 1 h and 6 weeks. Performance of the patient and control groups was matched at the immediate delay, which enabled comparisons of forgetting rate over the longer delays.
  
  
  RESULTS
  We found that TLE can affect the acquisition and retention of new memories over a relatively short delay of 1h. This deficit was associated with structural hippocampal abnormality, with a material-specific effect that was particularly evident for the verbal task. We also found evidence of accelerated long-term forgetting in both patient groups, for the verbal and non-verbal tasks. It was demonstrated most strongly on the verbal task by the patients with right lateralized hippocampal sclerosis whose verbal recall was normal at the 1-h delay. Accelerated long-term forgetting was not associated with hippocampal pathology, but was associated with the frequency of epileptic seizures.
  
  
  CONCLUSIONS
  The findings from the verbal task in particular provide evidence consistent with an extended period of memory consolidation that can be disrupted by both left and right TLE. The material-specific effects at the 1-h delay only, suggest that the initial consolidation of verbal and non-verbal, information depends on the integrity of the left and right hippocampus, respectively.
authors.affiliation: Department of Psychology, University of Chester, UK.
authors.forename: Heather
authors.initials: H
authors.lastname: Wilkinson
authors.forename: Juliet S
authors.initials: JS
authors.lastname: Holdstock
authors.forename: Gus
authors.initials: G
authors.lastname: Baker
authors.forename: Andrea
authors.initials: A
authors.lastname: Herbert
authors.forename: Fiona
authors.initials: F
authors.lastname: Clague
authors.forename: John J
authors.initials: JJ
authors.lastname: Downes
mesh_terms: D000328:Adult; D000679:Amygdala / Q000473:pathology; D000704:Analysis of Variance; D003627:Data Interpretation, Statistical; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000473:pathology / Q000523:psychology* / Q000601:surgery; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006624:Hippocampus / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D011939:Mental Recall; D019635:Neurosurgical Procedures; D011597:Psychomotor Performance / Q000502:physiology; D012598:Sclerosis; D013702:Temporal Lobe / Q000473:pathology; D014706:Verbal Learning / Q000502:physiology*